1. Field of the Invention
The present invention relates to a branch pipe joint and a method of connecting pipes using the branch pipe joint, and more particularly to a branch pipe joint having a number of connecting pipes, each having a different inner diameter, and to a method of connecting pipes using the above branch pipe joint.
2. Description of the Related Art
Conventionally, there has been widely used a multi-unit type air conditioner in which a plurality of indoor units are provided. The multi-unit type air conditioner carries out a refrigerating cycle and is schematically shown as 61 in FIG. 16. The air conditioner 61 is constituted by sequentially connecting a compressor 62, a four-way valve 63, an outdoor side heat exchanger 64, an outdoor side refrigerant controller 65, a branch pipe joint 66b, indoor side refrigerant controllers 67, a plurality of indoor side heat exchangers 68 (68a, 68b and 68c) and a branch pipe joint 66a. The branch pipe joint 66a is connected to the branch pipe joint 66b through the respective indoor side refrigerant controllers 67 and the indoor side heat exchangers 68 (68a, 68b and 68c). The branch pipe joint 66b has the same shape as that of the branch pipe joint 66a. In FIG. 16, the solid arrows indicate a flow direction of the refrigerant at the time of heating operation of the air conditioner, while the broken arrows indicate a flow direction of the refrigerant at the time of cooling operation.
As shown in FIGS. 17 and 18, each of the branch pipe joints 66 (66a and 66b) comprises a branch pipe joint body 67 having a cylindrical closed shape; a plurality of connecting pipes 68 welded to the branch pipe joint body 67 in a longitudinal direction thereof so with a constant interval p1 therebetween; and a common connecting pipe 69 welded to one end surface of the branch pipe joint body 67.
The plurality of the connecting pipes 68 are normally formed of copper tubes, and have the same shape. As shown in FIG. 19, each of the connecting pipes 68 has a pipe shape having multiple steps whose outer and inner diameters are gradually reduced in an axial direction. A first step portion 68a communicating with a welding root portion 68z has an inner diameter of 19.0 mm, a second step portion 68b communicating with the first step 68a has an inner diameter of 15.9 mm, a third step portion 68c communicating with the second step 68b has an inner diameter of 12.7 mm, and a fourth step portion 68d communicating with the third step portion 68c has an inner diameter of 9.5 mm, respectively.
Accordingly, when the air conditioner 61 shown in FIG. 16 is assembled using the branch pipe joint 66 at an installation site of the multi unit type air conditioner, the branch pipe joint 66, to which the plurality of connecting pipes 68 and the common connecting pipe 69 are welded, is prepared. Then, as shown in FIGS. 20 and 21, a position of each connecting pipe 68 having an inner diameter corresponding to an outer diameter of pipe 70 (70a, 70b) to be connected to the branch pipe joint 66 is selected, and the connecting pipe 68 is cut at that position by means of a pipe cutter. After an inner surface of the connecting pipe 68 is reshaped and finished, the pipe 70 is inserted into the connecting pipe and the connected portion is welded. In the case of the common connecting pipe 69, the same procedure is repeated, thereby to connect and weld a pipe 71 to the common connecting pipe 69.
However, in these cases, the connecting pipe 68 and the common connecting pipe 69 are cut at the installation site, so that copper powder is unavoidably generated and remains adhered to inner portions of the connecting pipe 68 and the common connecting pipe 69. When the air conditioner 61 is assembled and operated with the copper powder being adhered, blocking and jamming are liable to result at the outdoor side refrigerant controller 65, the indoor side refrigerant controller 67 or the like, which can constitute a cause of failure of the air conditioner 61.
Therefore, it has been necessarily required to clean the inner surfaces of the connecting pipes 68 and the common connecting pipe 69 after the connecting pipes 68 and the common connecting pipe 69 are cut, and to reshape the inner surfaces deformed by the pipe cutter, thus greatly increasing the work load for the assembly workers.
In addition, since the connecting pipe 68 is cut by means of the pipe cutter, it is required to provide a large pitch p1 of about 160 mm between the adjacent connecting pipes 68 so as to permit the pipe cutter to freely operate without any obstructions, so that the branch pipe joint 66 being formed must have a large size.